dimod.chain_break_frequency

chain_break_frequency(samples, embedding)

Determine the frequency of chain breaks in the given samples.

Parameters:

• samples (array-like/Response) – Matrix of samples or a dimod response object.
• embedding (dict) – Mapping from source graph to target graph as a dict of form {s: {t, …}, …}, where s is a source-model variable and t is a target-model variable.

Returns:

Frequency of chain breaks as a dict in the form {s: f, …}, where s is a variable in the source graph, and frequency, a float, is the fraction of broken chains.

Return type:

dict

Examples

This example embeds a single source node, ‘a’, as a chain of two target nodes (0, 1) and uses chain_break_frequency() to show that out of two synthetic samples, one ([-1, +1]) represents a broken chain.

>>> import dimod
>>> import numpy as np
>>> samples = np.matrix([[-1, +1], [+1, +1]])
>>> embedding = {'a': {0, 1}}
>>> print(dimod.chain_break_frequency(samples, embedding)['a'])
0.5

This example embeds a single source node (0) as a chain of two target nodes (a, b) and uses chain_break_frequency() to show that out of two samples in a dimod response, one ({‘a’: 1, ‘b’: 0}) represents a broken chain.

>>> import dimod
>>> response = dimod.Response.from_dicts([{'a': 1, 'b': 0}, {'a': 0, 'b': 0}], {'energy': [1, 0]})
>>> embedding = {0: {'a', 'b'}}
>>> print(dimod.chain_break_frequency(response, embedding)[0])
0.5